This invention relates in general to cushions and, more particularly, to cellular cushions having sealed cells.
Cushions find a wide variety of applications, but perhaps one of the most important is in connection with seating. Most chairs have soft seat surfaces and many have padded back rests as well. In some, the padding even extends along the hips and thighs of the user. Expanded polymer foam of a resilient character, such as polyurethane, is a popular cushioning material for seating and indeed finds widespread use in furniture and automotive seats. But resilient polymer foam does not produce the most desirable relationship between force and displacement. Far from this relationship being linear, it tends to be skewed such that the force increases at a greater rate than the displacement, and this makes the material unusually stiff when an individual or object is deeply immersed in it.
For those who are confined to wheelchairs, seat cushions represent a matter of considerable importance, for such individuals, due to their lack of mobility, have a tendency to develop pressure sores, particularly in the region of the ischia, which is the bony prominences of the buttocks. Indeed, special cushions exist for these individuals. One of the most effective is a cellular cushion sold under the trademark ROHO. It utilizes closely spaced air cells which are interconnected through the base of the cushion. One who sits upon such a cellular cushion becomes immersed in the array of air cells, all of which possess the same internal pressure, and thus his weight is distributed generally uniformly over the supporting surface formed by the array. U.S. Pat. No. 4,541,136 to R. H. Graebe shows a ROHO cellular cushion.
But the cellular cushion is somewhat bulky and is not needed in more conventional seating applications. Moreover, it requires inflation and thereafter adjustment to obtain the correct immersion for the user. Furthermore, it is expensive--indeed, too expensive for more conventional seating applications. Finally, it is used primarily as a seat cushion or mattress where it supports most or all of the user's weight. It finds little use as padding for a back rest or along the side of the user.
The present invention resides in a cellular cushion having its cells formed from an elastomeric material, and at least some of the cells are totally sealed and isolated from one another. The cushion, owing to the gas contained in its cells and the elastomeric constituency of the cells, has a linear relationship between force and displacement and is suited for use as a seat cushion or in other applications where impact or shock protection padding is required.